Spark plug and rotor assembly for a rotary combustion engine

ABSTRACT

A spark plug and rotor assembly for a rotary combustion engine having two rotor parts with mating interfaces with one rotor part having an integral phasing gear and the other rotor part being hollow and having an integral hub and an axially extending coolant passage therethrough and a spark plug for each chamber face of the rotor mounted in the interface of the hollow rotor part prior to joining this interface with the interface of the other rotor part.

Oct. 2, 1973 FOREIGN PATENTS OR APPLICATIONS I SPARK PLUG AND ROTOR ASSEMBLY FOR A ROTARY COMBUSTION ENGINE 927,704 6/1963 Great Britain..................... l23/8.0l

[75] Inventors: Parme G. Anthony, Centerville;

David Bond, Xenia both of Ohio Primary ExaminerCarlton R. Croyle General Motors Corporation, Casaregola Detroit Mich Attorney-J. L. Carpenter et al.

Assistant Examiner- [73] Assignee:

[57] ABSTRACT A spark plug and rotor assembly for a rotary combustion en [22] Filed: June 21, I972 Appl. No.: 264,915

gine having two rotor parts with mating interfaces with one rotor part having an integral phasing gear and the other rotor part being hollow and having an integral hub and an axially extending coolant passage therethrough and a spark plug for each chamber face of the rotor mounted in the interface of the hollow rotor part prior to joining this interface with the interface of the other rotor part.

0 8 8 B y I52 l d 1 w m 0 SF N! w 0 2 u C IN" n 3 e r m m -b-m 8 mm R m L .M l .m .w UIF H M M 555 5 UNITED STATES PATENTS l2/l958 123/8 09 418/120 3 Claims, 5 Drawing Figures 2,864,346 Taylor, Jr. 3,064,880 ll/l 962 Wankel et PATENTEDBBT ems SHEET 1 [IF 2 1 SPARK PLUG AND ROTOR ASSEMBLY FOR A ROTARY COMBUSTION ENGINE This invention relates to a spark plug and rotor assembly for a rotary combustion engine and more particularly to permanent integration of the spark plugs into a rotor.

In rotary combustion engines of the Wankel type, it is present commercial practice to have one or more conventional spark plugs mounted in the engine housing with each spark plug electrode exposed through a shooter hole to the rotor cavity to ignite fuel in the engines working chambers that are spaced about and move with the engines rotor. Where the rotors apex seals traverse a spark plug shooter hole, there results a leak path for the compressed gases which lowers engine efficiency. Furthermore, when a spark plug is located in the rotor housing there is a loss of cooling and a resulting hot spot in this area due to the spark plug boss. One way of avoiding such gas leakage and also this hot spot in the housing is to mount spark plugs on the rotor wherein there is at least one spark plug for every rotor face or flank. However, in attempting to locate the spark plugs on the rotor, it has been found that conventional spark plugs with their attendant mounting bosses substantially complicate the construction of the rotor itself in addition to adding considerable mass that requires cooling and lowers the rotor speed limit.

The spark plug and rotor assembly according to the present invention comprises a pair of separately formed metal rotor parts having mating interfaces. One of these rotor parts has an integral hub portion determining an axis about which the rotor rotates with this hub portion and the peripheral face portions of this one rotor part having axially extending space therebetween for the passage of coolant through the rotor when the two rotor parts are mated. The other rotor part has an internal toothed gear concentric with the hub portion of the other rotor part to which it is later joined at the interfaces. The interface of the hollow rotor part has a spark plug recess for every face portion or flank that opens to one face portion and a spark plug is mounted in and fills each of these spark plug recesses in the interface of the hollow rotor part. Each spark plug comprises a high voltage wire or electrode which is encased in a ceramic body that is covered by a thin layer of metal with the electrode having a terminal end for receiving an electrical ignition pulse and a spark end projecting out through the opening past the rotor face portion and spaced a spark distance from a rotor grounded electrode. With these spark plugs in position in the recesses in the hollow rotor part, the two rotor parts are then mated and they and the spark plugs are brazed at their seams to provide an integral construction. Where more than one spark is desired for each working chamber, the ceramic body of each spark plug has a branch extending therefrom leading out another opening in the rotor face peripherally spaced from the other opening therethrough. In the multispark spark plug a second electrode extends through the branch with one spark end spaced aspark distance from the spark end of the first electrode and another spark end projecting out through the other opening past the rotor face portion spaced a spark distance from the grounded electrode. As compared with conventional spark plugs, this integration of the present spark plugs adds considerably less mass, yet the rotor is simple and easy to manufacture which contributes to reducing cost.

An object of the present invention is to provide a new and improved spark plug-and rotor assembly for a rotary combustion engine.

Another object is to provide for a rotary combustion engine a two-piece rotor with an integral spark plug for each rotor face integrated with the rotor construction.

Another object is to provide a spark plug and multipiece rotor assembly for a rotary combustion engine which combines a spark plug at each rotor face during rotor fabrication wherein each spark plug comprises an electrode encased in a ceramic body which is covered by a layer of material that is bonded between the rotor parts.

Another object is to provide an integral spark plug and rotor construction wherein one of two rotor parts having mating interfaces has a spark plug recess in its interface receiving a spark plug for every rotor face which is joined to the rotor parts when they are joined.

These and other objects of the present invention will become more apparent from the following description and drawing in which:

FIG. 1 is a partial view of a rotary combustion engine having a spark plug and rotor assembly according to the present invention with parts broken away'to show certain details of construction.

FIG. 2 is a partial view of the spark plug and rotor assembly along the line 22 in FIG. 1.

FIG. 3 is a partial view of the spark plug and rotor assembly along the line 3-3 in FIG. 1.

FIG. 4 is an exploded view of the spark plug and rotor assembly of FIG. 1.

FIG. 5 is a perspective view of the rotors crankshaft in FIG. 1 with portions of the ignition system shown schematically.

Referring to FIG. 1, the spark plug and rotor assembly according to the present invention is illustrated for use in a rotary combustion engine of the Wankel type comprising a stationary outer body or housing 10. The housing 10 has a cavity 11 that is defined by an inwardly facing peripheral wall 12 and a pair of axially spaced opposed end walls 14 of which only one is shown. The peripheral wall 12 is in the shape of a twolobed epitrochoid or a curve parallel thereto whose center is indicated at 16. A crankshaft 18 extends through the cavity 11 and is rotatably supported by the housing 10 in the end walls 14 so that the shaft axis is coincident with a line through the center l6which is parallel to the peripheral wall 12.

The crankshaft 18 is provided in the cavity 11 with an eccentric 21 on which a rotor is mounted for rotation about the eccentrics center line24 which is thus the rotors axis, the rotor being provided with'a sleeve bearing 23 for this mounting. The rotor 22 whose details of construction will be described in detail later has the general shape of a triangle with three flanks or faces 26 which are convex and face the peripheral wall 12 and cooperate therewith and with the end walls to define three variable volume working chambers 28. An apex seal 29 is mounted at each apex or corner of rotor 22 and extends the width thereof and three pairs of side seals 30 are mounted in each rotor side and arranged to extend between the apex seals 29 with three corner seals 31 mounted in each rotor side providing sealing links between the ends of the side seals and the apex seals.

The apex seals 29 are urged by biasing means not shown to continuously engage the periperal wall 12 and both the side seals 30 and corner seals 31 are urged by biasing means not shown to continuously engage the end walls 14 with the complete seal arrangement acting to seal the chambers 28. With the two-lobed peripheral wall 12 and the three-lobed rotor 22 there is made available the four phases of intake, compression, expansion and exhaust in each chamber for each rotor revolution in fixed relation to the housing by forcing the rotor to rotate at one-third the speed of the output shaft. This is accomplished by a gear train comprising an internally toothed gear 32 which is fixed to and concentric with the rotor 22. The gear 32 meshes with an externally toothed annular gear 33 which is received about and is concentric with the crankshaft and is made stationary by being fixed to the engine housing at one of the end walls 14. The gear 32 has one and onehalf times the number of teeth as the gear 33 to provide the required ratio of 3:1 between the crankshaft 18 and the rotor 22. An air-fuel mixture from a suitable carburetor arrangement, not shown, is made available to each chamber 28 by an intake passage 34 that extends through the housing 10 and opens to .the cavity 11 through the end walls 14 at axially opposite locations, this porting to the cavity being located to one side of the peripheral walls cusp 36. The exhaust products of combustion are delivered from each chamber 28 by an exhaust passage 37 which extends through the housing 10 and opens to the cavity 11 through the peripheral wall 12 on the other side of cusp 36. A single channel or recess 38 is provided in the center of each chamber face 26 of the rotor 22 to provide for the transfer of working gases past the peripheral walls other cusp 39 when a rotor face is at or near a top-dead-center position as shown in FIG. 1 so that a chamber is not divided by cusp 39 at the time when combustion is occurring therein.

The engine construction thus far described is conventional. Typically, such engines have each of the three working chambers undergoing intake, compression, expansion and exhaust with a single rotor arrangement as shown in FIG. 1 providing a power phase for each revolution of the crankshaft. As the rotor rotates in the direction of the arrow in FIG. 1, the air-fuel mixture is periodically successively drawn into the working chambers 28 by the side seals 30 traversing the intake passage 34. The fuel mixture is then trapped in each working chamber and compressed and when the rotor is in the vicinity of top-dead-center, this mixture is ignited. It is present commercial practice to have either one or two spark plugs located in the rotor housing 10 near the cusp 39 with their electrodes exposed in the cavity 11 to the passing working chambers for the ignition. Upon ignition of the mixture in the working chambers, the peripheral wall takes the reaction forcing the rotor to continue rotation while the gas is expanding. The leading apex seal of each of the working chambers successively traverse the exhaust passage 37 and the exhaust products are then expelled to the atmosphere to complete the cycle.

Describing now the spark plug and rotor construction according to the present invention with the attendant ignition circuit, the rotor 22 as shown in FIGS. 1, 2, 3 and 4, has only two rotor parts 40 and 41 which are preferably made of powdered metal. The rotor parts 40 and 41 have outboard sides 42 and 44 and mating interfaces 46 and 47, respectively, which are all perpendicular to the rotor's axis 24. The interfaces 46 and 47 are pan split off-center width-wise of the rotor with the rotor part 40 being of generally hollow construction and constituting the larger part and the other rotor part 41 being of solid construction and constituting the small part. The hollow rotor part 40 has a peripheral wall 48 and a central hub portion 49 which receives the sleeve bearing 23 and is joined to the peripheral wall 48 by radially extending ribs 52 which leave axially extending spaces 54 between the hub portion 49 and the peripheral wall 48 for the passage of coolant in an axial direction through the rotor when the rotor parts are joined as shown in FIG. 3. The solid rotor part 41 has an internal toothed gear 32 formed integral therewith concentric with the rotor axis 24.

Describing now the spark plug construction and mounting in the rotor assembly, the interface 46 of the hollow rotor part 40 has in each angular segment between two rotor apexes a spark plug recess arrangement comprising a centrally located spark plug recess 56 in the peripheral wall 48 at the bottom of the channel 38 and another spark plug recess 58 in the peripheral wall intermediate the centrally located recess 56 and the trailing rotor apex with both these recesses opening through the associated rotor face portion. Furthermore, there is provided in the interface 46 a recess 59 in the rib 52 between the two recesses 56 and 58. In addition, there is provided a recess 60 in one end of the hub portion 49 which is radially aligned with the recess 56 and opens to a recess 62 that is formed in the interior of the hub portion 49 and extends the width thereof parallel to the rotor axis 24. The recesses 56, 58,59, 60 and 62 in each of the angular segments cooperatively provide an accommodating recess for a spark plug 66.

Each spark plug 66 comprises a ceramic body 68 which as best shown in FIGS. 1, 3 and 4 includes a trunk 69 with a base portion 70 which is received in one of the recesses 60 and a top portion 71 which is received in the radially outward leading recess 56. The trunk 69 has a branch 74 extending from between the base portion 70 and the top portion 71 which is received at an intermediate area in the rib recess 59 and has a tip portion 76 that is received in the trailing recess 58. In addition, the base portion 70 of the ceramic body has a root 78 that is received in the hub recess 62 and extends the length thereof. The ceramic body except for the trunk top, branch tip and root end and at least in those areas where it is received in the recesses in the interface 46 and is engaged by the opposite interface 47 of the other rotor part, is coated with a metal layer 79 that is bondable to the metal of the rotor parts with the dimensions of these metal coated spark plug portions received in the recesses in the interface being sized so that the accommodating recesses are completely filled and thus sealed by the bonding.

Three electrodes 80, 81 and 82 of high voltage wire are molded in place in each spark plugs ceramic body. As best shown in FIG. 3, the electrode extends through the trunk 69 and the root 78 with a terminal 83 projecting out through the root tip and a spark end 84 projecting out through the trunk top past the rotor face 26 into the channel-38.-The electrode 81 extends from the trunk 69 through the branch 74 and has one spark end 86 projecting out through the trunk top and spaced a spark distance from the spark end 84 of the electrode 80. The electrode 81 has at its opposite end a spark end 88 projecting out through the branch tip I into a cup-shaped depression 90 in the rotor face so that this spark end will not rub or spark against the peripheral wall 12. The third electrode '82 as shown in FIG. 2 has a ground portion 94 extending out from the branch 74 grounded to the rotor in the recess 58 and a spark end 96 that is spaced a spark distance from the spark end 88 of the electrode 81. This multielectrode arrangement having a leading spark gap 98 between the spark ends 84 and 86 and a trailing spark gap 100 be tween spark ends 88 and 96 is of the type disclosed in US. Pat. application Ser. No. 211,429 entitled Rotary Combustion Engine Ignition by Harvey A. Burley and assigned to the assignee of the present invention, which is hereby incorporated by reference. In such an arrangement with the capacitance across the leading gap considerably less than that across the trailing gap to ground, a greater percentage of the applied voltage appears across the leading gap to effect electrical breakdown and when this gap has been bridged all of the applied voltage except for the small amount in the plasma of the leading gap appears across the trailing gap and this gap also is quickly bridged with the double gap breakdown taking place almost simultaneously. Furthermore, with this location of the spark gaps the leading spark may be made to occur in the vicinity of topdead-center at a mid point in the chamber and the trailing spark occurs near the trailing end of the chamber a very short time later. For a more detailed understanding of such a multispark electrode arrangement and the variations thereof, reference should be made to the Burley application. It will also be understood that the spark plugs may provide a single spark with only two electrodes wherein one of these is grounded to the ro- In assembling the rotor, the three spark plugs 66 are first mounted in their accommodating recesses in the interface 46 of the hollow rotor part 40. With the spark plugs 66 in place, the solid rotor part 41 is then positioned in its mating relationship with the rotor part 40. Then their mating interfaces 46 and 47 and also the mating surfaces of the spark plugs metal coatings and these rotor parts are brazed together with a suitable brazing material. The resulting spark plug and rotor structure has a gas tight seam in the rotor faces between the rotor parts and around the spark plugs where they project through the rotor faces.

Referring to FIG. 5, voltage is provided to the spark plugs 66 by a high voltage insulated wire 102 which extends through an axial passage in the crankshaft 18 and out through a radial opening the side of eccentric 21 opposite where the gearing is located. A rotary disc 104 suitably mounted for rotation coaxial with the crankshaft 18 is connected to receive voltage from a suitable conventional ignition control 106 which is powered by a D. C. power source 108. Disc 104 has a contact 110 from which electrical ignition pulses from the ignition control jump to a terminal 112 that is connected to wire 102, the terminal 112 being mounted on the end of the crankshaft by a mount 114 of nonconducting material. The electrical ignition pulses are conducted by the wire 102 to an arcuate shaped metal conductor 116 which is mounted in one interior side of an arcuate channel member 118 of nonconducting material that is secured to the crankshaft so as to center the contact strip 116 with the top-dead-center position of the eccentric 21. As shown in FIG. 3, the terminal end 81 of each of the spark plugs 66 extends radially past the rotor body into the channel .120 so that it brushes the contact strip 116 as the crankshaft rotates when each rotor face is in the vicinity of top-dead-center. Thus, an electrical ignition pulse from the contact strip 116 is led to the appropriate spark plug 66, the length of the contact strip being such that voltage then can be applied for sparking over a relatively large angle to provide for ignition timing changes.

The above described embodiment is illustrative of the invention which may be modified within the scope of the appended claims.

We claim:

1. A spark plug and rotor assembly for a rotary combustion engine comprising a pair of rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of said rotor parts having a hub portion determining an axis about which said rotor parts rotate, said interfaces transverse to said axis, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having a spark plug recess for and open to every face portion of said one rotor part, spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body received in and having a shape to fill one spark plug recess, a first electrode in each said ceramic body having a terminal at one end for receiving an electrical ignition pulse and a spark end at the other end projecting out past the associated face portion, a second electrode in each said ceramic body operatively grounded to said rotor and having a spark end projecting out past the associated face portion and spaced a spark distance from said spark end of said first electrode, and means permanently joining said mating rotor parts and said spark plug means where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part.

2. A spark plug and rotor assembly fora rotary combustion engine comprising a pair of metal rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of saidrotor parts having a hub portion determining an axis about which said rotor parts rotate,

said interfaces perpendicular to said axis, said one rotor part having axially extending pasages therethrough for the passage of coolant when said rotor parts are joined, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having a recess open to every face portion of said one rotor part, an opening through said hub portion for every face portion, spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body having a trunk with a base portion received in and having a shape that fills one of said openings in said hub portion and with a top portion received in and having a shape that fills one of said recesses open to one of said face portions, a first electrode in each said ceramic body extending through said trunk having a terminal for receiving an electrical ignition pulse and a spark end projecting out through said top portion, a second electrode in each said ceramic body operatively grounded to said rotor having a spark end projecting out through said top portion and spaced a spark distance from said spark end of said first electrode, and means permanently joining said mating rotor parts and said spark plug where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part.

3. A spark plug and rotor assembly for a rotary combustion engine comprising a pair of metal rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of said rotor parts having a hub portion determining an axis about which said rotor parts rotate, said interfaces perpendicular to said axis, said one rotor part having axially extending passages therethrough for the passage of coolant when said rotor parts are joined, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having two recesses spaced angularly about said axis and open to every face portion of said one rotor part, an opening through said hub portion for every face portion, multielectrode spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body having a trunk with a base portion received in one of said openings in said hub portion and with a top portion received in and having a shape that fills one of said recesses open to one of said face portions, said trunk having a branch portion extending from between said base portion and said top portion with a tip portion received in and having a shape that fills another of said recesses open to said one face portion, a first electrode in each said ceramic body extending through said trunk having a terminal for receiving an electrical ignition pulse and a spark end projecting out through said top portion past the associated face portion, a second electrode in each said ceramic body extending from said trunk through said branch having one spark end projecting out through said top portion and spaced a spark distance from said spark end of said first electrode and having another spark end projecting out through said tip portion past the associated face portion, a third electrode in each said ceramic body having a ground portion extending out through said branch grounded to said rotor and a spark end projecting out through said tip portion and spaced a spark distance from said other spark end of said second electrode, and means permanently joining said mating rotor parts and said spark plug means where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part. 

1. A spark plug and rotor assembly for a rotary combustion engine comprising a pair of rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of said rotor parts having a hub portion determining an axis about which said rotor parts rotate, said interfaces transverse to said axis, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having a spark plug recess for and open to every face portion of said one rotor part, spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body received in and having a shape to fill one spark plug recess, a first electrode in each said ceramic body having a terminal at one end for receiving aN electrical ignition pulse and a spark end at the other end projecting out past the associated face portion, a second electrode in each said ceramic body operatively grounded to said rotor and having a spark end projecting out past the associated face portion and spaced a spark distance from said spark end of said first electrode, and means permanently joining said mating rotor parts and said spark plug means where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part.
 2. A spark plug and rotor assembly for a rotary combustion engine comprising a pair of metal rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of said rotor parts having a hub portion determining an axis about which said rotor parts rotate, said interfaces perpendicular to said axis, said one rotor part having axially extending pasages therethrough for the passage of coolant when said rotor parts are joined, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having a recess open to every face portion of said one rotor part, an opening through said hub portion for every face portion, spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body having a trunk with a base portion received in and having a shape that fills one of said openings in said hub portion and with a top portion received in and having a shape that fills one of said recesses open to one of said face portions, a first electrode in each said ceramic body extending through said trunk having a terminal for receiving an electrical ignition pulse and a spark end projecting out through said top portion, a second electrode in each said ceramic body operatively grounded to said rotor having a spark end projecting out through said top portion and spaced a spark distance from said spark end of said first electrode, and means permanently joining said mating rotor parts and said spark plug where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part.
 3. A spark plug and rotor assembly for a rotary combustion engine comprising a pair of metal rotor parts having mating peripheral face portions that cooperate to define peripheral rotor faces and also having mating interfaces, one of said rotor parts having a hub portion determining an axis about which said rotor parts rotate, said interfaces perpendicular to said axis, said one rotor part having axially extending passages therethrough for the passage of coolant when said rotor parts are joined, the other of said rotor parts having an internal toothed gear concentric with said hub portion, the interface of said one rotor part having two recesses spaced angularly about said axis and open to every face portion of said one rotor part, an opening through said hub portion for every face portion, multielectrode spark plug means for each said rotor face, each said spark plug means comprising a metal coated ceramic body having a trunk with a base portion received in one of said openings in said hub portion and with a top portion received in and having a shape that fills one of said recesses open to one of said face portions, said trunk having a branch portion extending from between said base portion and said top portion with a tip portion received in and having a shape that fills another of said recesses open to said one face portion, a first electrode in each said ceramic body extending through said trunk having a terminal for receiving an electrical ignition pulse and a spark end projecting out through said top portion past the associated face portion, a second electrode in each said ceramic body extending from said trunk through said branch having one spark end projecting out through said top portion and spaced a spark distance from said spark end of said first electrode and having anotheR spark end projecting out through said tip portion past the associated face portion, a third electrode in each said ceramic body having a ground portion extending out through said branch grounded to said rotor and a spark end projecting out through said tip portion and spaced a spark distance from said other spark end of said second electrode, and means permanently joining said mating rotor parts and said spark plug means where they have metal-to-metal contact with said spark plug means mounted in the interface of said one rotor part. 